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#Serial cloner linear to circular full#Writing to a full FIFO would also be an error, as valid data waiting in the queue would be overwritten by newer data. Reading from an empty FIFO would be an error, as a random data word would be accepted as valid data. The algorithm for FIFO operation consists of only three procedures: 1. In most commercial designs, only the smallest FIFOs would use a register file, as the power savings of using a memory cell would override the other concerns for larger applications. Accordingly, the register file will be modified to have a data input port and a data output port. The register file developed in previous chapters uses a single bidirectional data port, but that would not be suitable for a FIFO, as that would require arbitrating access to the port and would make simultaneous reads and writes impossible. While a dual-port memory is often used for FIFOs, a register file simplifies the design. Being made of flipflops, each cell naturally has an input port and an output port, exactly what is needed for a FIFO. Although register files have the disadvantages of being larger and more power hungry than memory cells, they have the advantages of being synthesizable without any additional tools and matching perfectly to the needs of a FIFO. The FIFO model developed in this section will use a register file rather than a RAM cell. The memory cell is also likely to be the component that limits the FIFO’s operating speed, so the FIFO in all probability will be as fast as memory technology allows. A circular buffer FIFO is as deep and wide as the memory cell it uses. With such a design, the speed is nearly independent from the size, unlike a true FIFO, where speed is inversely proportional to depth. This saves the time of having to check for the end of the buffer and resetting the pointer if the end is reached.įigure 7.23. Writing to the correct memory is then ensured. A circular buffer can be written so that when the end of the allocated input buffer is reached, the pointer automatically wraps around to the beginning of the buffer. MOV #0, CDP starting offset for circular bufferīSET CDPLC set circular instead of linearĪnother example where circular buffers are useful is when working with individual inputs and only saving the last N inputs. MOV #a0, BSAC starting address of circular buffer #Serial cloner linear to circular code#Here is the code to set up a circular buffer:ĪMOV #a0, XCDP coefficient data pointer Setting up circular buffers usually involves writing to some registers to tell the DSP the buffer start address, buffer size, and a bit to tell the DSP to use circular buffers. #Serial cloner linear to circular update#Therefore, the time that it takes to update the pointers is saved. Using circular buffering, the coefficient pointer will automatically wrap around to the beginning when the end of the loop is encountered. In the filter example, all the coefficients are processed, and then the coefficient pointer is reset when the loop is finished. Robert Oshana, in DSP for Embedded and Real-Time Systems, 2012 Circular buffersĬircular buffers are useful in DSP programming because most implementations include a loop of some sort. ![]()
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